The present invention relates to removal or harvesting of body vessels, and, in one application, to a device and method for assisting in a saphenous vein graft harvesting procedure.
Vessels have been removed from patients for various reasons. Diseased varicose veins have been removed, typically from a patient""s legs. Vessels have been harvested to provide a vessel graft. In one common procedure, saphenous veins are harvested for use as a vessel graft to bypass clogged coronary arteries.
The saphenous vein is located within a subcutaneous layer along a patient""s inner thigh to the lower limb. In saphenous vein graft harvesting for coronary artery bypass procedures, the saphenous vein is removed from the patient and used as a graft to bypass occluded arteries. Saphenous veins graft harvesting has been accomplished in both open and endoscopic procedures. In an open procedure, typically a long incision is made along the inner thigh from the groin to the knee and possibly along the lower portion of the leg as well. The main vessel is ligated and various tributary vessels along the length of the vessel are ligated. The vessel is separated or dissected away from surrounding tissue, which may include fibrous tissue and connective tissue. Various cutting, dissecting and tissue separating instruments may be used for this purpose. After ligating and separating the vessel, it is transected and removed and prepared for use as a graft. In the open procedures, saphenous vein graft harvesting is highly traumatic and invasive, causing significant, and frequently persistent, post operative pain, and requiring significant time for recovery. Wound break down, infections and other complications commonly result from the saphenous vein graft harvesting. It is believed that some of the reasons for complications in such procedures are, the length of the incision, the dehydration of the subcutaneous fatty layer from prolonged exposure to air during dissection of the vessel, the density of the tissue requiring significant dissection, and the already debilitated status of many of the patents.
Endoscopic techniques have been developed to reduce trauma from the incision. The endoscopic procedures, like the open procedures, also strive to ligate the main vessel and its tributaries and to separate the vessel from surrounding tissue before removing the vessel. An incision is made on the inner thigh near the knee, and the saphenous vein is identified and isolated. In one procedure, the area along the vessel is insufflated with a gas such as CO2, and using a blunt tip trocar, to provide a working area. Other instruments and procedures have been proposed to provide such working space and to further separate the vein from surrounding tissue. Such instruments and procedures have included, for example, initially using an optical dissector, other blunt dissector or cannula to dissect or separate tissue from the superior surface of the vein. Then, e.g., using a balloon expandable member to further separate tissue, or using an optical retractor to retract dissected tissue away from the superior surface of the vessel, additional subcutaneous space is created. Typically, endoscopically guided instruments are used to separate the vein from surrounding tissue as the instruments are maneuvered along the length of the vein while side branches or tributaries of the vein are dissected, ligated and then transected to permit removal of the vein. The endoscopic procedure in general, entails using some form of visualization of the procedure that is performed through small incisions. However, because of the dense nature of the subcutaneous tissues in this area in many people, the tissue separation can be difficult, leading to bleeding that further restricts visualization in the procedure, and tissue trauma and bruising including injury to the vessel making it less suitable as a graft. Due to the denseness of the tissue, along with the resulting difficulty in maneuvering and visualizing the procedure, endoscopic harvesting has had limited success and frequently during such procedure, the endoscopic instruments are abandoned and the surgeon will resort to an open procedure.
Accordingly it would be desirable to provide instruments and methods for removing vessels and in particular for saphenous vein graft harvesting in either an open or endoscopic procedure that reduce tissue trauma, provide easier separation of the vein from the surrounding tissue, and improve recovery.
A method and system for removing body vessels from a patient is provided. An embodiment of the method includes a method for harvesting a vessel for subsequent use in a grafting procedure, such as, for example, saphenous vein graft harvesting for a coronary bypass surgical operation. According to on embodiment, a quantity of a solution is infused into tissue surrounding the portion of the vessel to be removed. An external device is used to apply an energy field to the tissue to loosen the intercellular connections between the tissue and the vessel to be removed. One such device is an ultrasonic instrument having an ultrasonic transducer comprised of a composite of ultrasonic crystal transducers. Once the energy field has been applied, the portion of the vessel to be removed is separated from surrounding tissue and tributary vessels are ligated. The portion of the vessel is then transected and removed from the body. It is believed that the procedure will be less traumatic by decreasing time required to perform the dissection and ligation portions of the procedure and by decreasing bleeding, tissue tearing, post operative pain and complications.
One embodiment of the present invention provides a system and method for preparing the fibrous and connective tissue surrounding the vessel by warming and softening the tissue using an externally applied energy source directed through the skin to the surgical site, in combination with infusing a solution in the tissue surrounding the surgical site. It is believed the procedure will decrease bleeding and minimize bruising and tissue trauma. The procedure of the present invention is particularly suitable for removing vessels that lie within the subcutaneous tissue layer. In one embodiment, the procedure is used for saphenous vein graft harvesting.
According to an embodiment of the invention, the skin tissue is initially prepared by infusing a solution of normal saline that has been mixed with a small amount of lidocaine and epinephrine under the skin in a subcutaneous layer. An external ultrasound device is used to apply ultrasonic energy to the skin for approximately around 2-5 minutes. The ultrasonic energy loosens the layer of skin and surrounding tissue permitting easier passage of surgical instruments and improving the accuracy as well as the ease and efficiency. Once the tissue has been infused and the energy applied, in an open or endoscopic procedure, the vessel is then separated from the surrounding tissue; ligated (including from all the tributary vessels); and transected from the remaining vessels and tributaries. The vessel is then removed. Known surgical techniques may be used for tissue separation, dissection, ligation and transection.
It is believed that the ultrasonic energy as applied will loosen intercellular connections, i.e., connections between the vessel and surrounding tissue whether it be connective tissue of e.g., fibrous tissue held by hydrostatic pressure. The infused fluid acts as a medium through which the ultrasonic energy can place a field around the vessel and attenuate to some degree, the ultrasonic energy and possible resulting tissue damage. It is believed that through cavitation and microstreaming (i.e., movement of the fluid in a linear direction away from the ultrasonic energy source), intracellular connections are loosened, tissue viscosity is decreased, and the tissue becomes super hydrated with minimal destruction of cells allowing dissection to proceed much more easily. Additional benefits provide better viewing of the surgical site due to reduced bleeding from tearing of dense tissue surrounding the vessel and tributaries from the main vessel. In an open technique, superhydrating the tissues reduces the undesired effects of tissue dehydration during the open procedure whether initially performed as an open procedure or where the endoscopic procedure is abandoned in favor of an open procedure. By infusing fluid in an applying the energy, fluid is infused into subcutaneous interstitial space.
The procedure described herein may be used in other applications other than saphenous vein graft harvesting or vessel harvesting. The procedure, for example, may be used to remove diseased veins such as varicose veins.
Other energy forms may be used other than ultrasonic energy to achieve a desired result. The energy may be in the form of other acoustic waves or mechanical pressure waves. The energy may also be in the form of electromagnetic energy, e.g., columnated light or a low level laser such as an Erchonia(trademark) laser device. Other energies that translate into a kinetic energy in the infused solution with minimal damage to surrounding tissue may be used.